From: Oleg Nesterov <oleg@tv-sign.ru>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@osdl.org>,
linux-kernel@vger.kernel.org, Dave Hansen <haveblue@us.ibm.com>,
Herbert Poetzl <herbert@13thfloor.at>
Subject: Re: [PATCH] pidhash: Kill switch_exec_pids
Date: Thu, 02 Feb 2006 23:25:21 +0300 [thread overview]
Message-ID: <43E26AB1.8509A175@tv-sign.ru> (raw)
In-Reply-To: <m1r76lslhi.fsf@ebiederm.dsl.xmission.com>
Eric W. Biederman wrote:
>
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -699,7 +699,17 @@ static int de_thread(struct task_struct
> remove_parent(current);
> remove_parent(leader);
>
> - switch_exec_pids(leader, current);
> +
> + /* Become a process group leader with the old leader's pid.
> + * Note: The old leader also uses thispid until release_task
> + * is called. Odd but simple and correct.
> + */
> + detach_pid(current, PIDTYPE_PID);
> + current->pid = leader->pid;
> + attach_pid(current, PIDTYPE_PID, current->pid);
What happens after de_thread() unlocks tasklist_lock and before
it is taken again in release_task() ?
In that window find_task_by_pid() will return dead leader, not
the new leader of thread group. This means we can miss tkill()
or ptrace(), for example.
Oleg.
next prev parent reply other threads:[~2006-02-02 19:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-02 17:45 Eric W. Biederman
2006-02-02 20:25 ` Oleg Nesterov [this message]
2006-02-02 20:08 ` Eric W. Biederman
2006-02-03 13:26 ` Oleg Nesterov
2006-02-03 12:59 ` Eric W. Biederman
2006-02-02 21:45 ` Andrew Morton
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